I download a lot of trustworthy content from the internet. I also know when I am downloading content from the Internet. Thus, I don’t need a warning telling me that I have downloaded content from the Internet.
Apple has a warning system when you first try to open a file that has been downloaded from the internet.
I found it particularly annoying when trying to download endnote references from Google Scholar, and every time, I would have to respond to the warning message instead of automatically incorporating the file into my Endnote library.
This MacWorld post shows how to disable the warning system both temporarily and completely.
In particular, the following entered at the terminal followed by a Mac restart removes the warning.
defaults write com.apple.LaunchServices LSQuarantine -bool NO